1. Field of the Invention
The present invention relates to a monitoring apparatus, a monitoring method, a monitoring program and a monitoring program recorded recording medium readable by a computer. Particularly, the invention relates to the monitoring apparatus for finding and tracking an object intruded in an area to be monitored, the monitoring method, the monitoring program and the monitoring program recorded recording medium readable by a computer.
2. Description of the Related Art
Conventionally, a monitoring apparatus for finding an object (including a person) intruded in an area to be monitored is known. The conventional monitoring apparatus processes an image obtained by capturing an image of an area to be monitored, so as to detect (find) an object intruded in the monitoring area. Such a kind of the monitoring apparatus executes a process for finding an intruded object and a tracking process for changing an image taking direction of a camera so that the found object is within the image capturing area and simultaneously capturing an image of the object.
In addition, such a monitoring apparatus can be remotely controlled in a place where a user has gone separated from a house where the monitoring apparatus is installed. For example, a mobile information terminal is connected with the monitoring apparatus via a public line from a place where the user has gone and a predetermined remote control command is transmitted to the monitoring apparatus, so that the monitoring apparatus can be controlled from the information terminal. The monitoring apparatus is remotely controlled in such a manner, so that a condition in the house captured by the monitoring apparatus can be watched in the place where the user has gone.
Such a conventional monitoring apparatus performs an operation for finding an object intruded in a monitoring area, an operation for tracking the found object, an operation for recording an image obtained by capturing an image of the found object, an operation for amply capturing an image of the found object, and the like. However, in the case where such a conventional monitoring apparatus receives the remote control command from the information terminal connected with the monitoring apparatus even while it is performing the monitoring operation, it executes the remote control command. For this reason, while the monitoring apparatus is finding the object and recording its image, it receives the remote control command, thereby arising a problem that the recording is stopped and important information is not recorded.
In addition, as a technique for detecting an object from an captured image in the conventional monitoring apparatus, (1) a background image differential process, (2) a color extracting process and (3) a time differential process are known.
In the background image differential process (1), a background area is previously specified, and an image of the background area is captured by the monitoring apparatus to be stored. Then, the monitoring apparatus captures a current image of the background area and detects an area which does not exist in the stored background image based upon a difference between the current image of the background area and the stored image of the background area. This process has an advantage that even a still object can be detected, but it has a disadvantage such that-in the case where an environment such as an illumination or a sunlight is different between a point of time at which the background image has been previously captured and the current point of time, an entire image is different, and thus accurate detection cannot be executed.
(2) The color extracting process detects a specified color, for example, a skin color of a person from an image. Since a specified color which has been preset is extracted from an image, the process has an advantage that an area of the specified color can be extracted accurately. However, it has a disadvantage that only a specified color which has been preset can be extracted.
(3) The time differential process calculates a difference between a plurality of images captured at predetermined comparatively short time intervals and detects an area where a change occurs. Since images which has been captured at comparatively shorter intervals than that in the background image differential process, this process has an advantage that it is hardly influenced by a change in environment. However, on the contrary, since images captured at short intervals are compared with one another, this process has a disadvantage that a still object which hardly move for the short intervals cannot be detected.
Namely, the conventional monitor apparatus uses only one of the above-mentioned image processes, it has a problem of detecting accuracy. Namely, the monitoring apparatus using the background differential process has the problem that an object cannot be detected accurately in a monitoring area where a change in environment is intensive. The monitoring apparatus using the color extracting process has a problem that an object having a color different from a predetermined color cannot be detected. The monitoring apparatus using the time differential process has a problem that a still object cannot be detected.
Further, in the case where after an object position is detected by the background image differential process, the found object is tried to be tracked, the object position in a next position cannot be detected if a background image for the object position is not previously obtained. For this reason, background images from various directions should be previously obtained. As a result, there arises a problem that a storage capacity of the background images becomes enormous.
Therefore, the conventional monitoring apparatus adopts a time difference tracking method of, after detecting an area of a moving object by means of the time differential process, tracking the area. In the time difference tracking, since it is not necessary to previously store a background image, it is not necessary to store a lot of background images. However, in the time difference tracking, when an object stops, a difference cannot be obtained, thereby still arising a problem that the object position cannot be detected.